When fluids are produced from a petroleum well, gas and liquids are frequently separated at a production facility serving the entire field or a group of wells. Other functions occurring at production facilities include gas processing and compression. Compressed gas may then be reinjected into a subterranean formation.
Oil with a high gas to oil ratio (GOR) increases the handling costs for production facilities and gas injection systems. In some fields, the available gas compression capacity of the production facility or regulations restricting the quantity of gas that can be produced limit the total number of wells in production. Thus, if a portion of the gas from a high GOR well can be separated before the produced hydrocarbons reach the production facility, the effective GOR can be lowered, and other previously shut-in wells elsewhere in the field can be produced or the volume of oil which is permitted to be produced from a well can be increased.
In an oil field undergoing pressure maintenance operations, compressed produced gas can be injected into the same reservoir from which fluids are produced. In other situations, disposal of gas produced at isolated wells can pose a problem where it is uneconomical to tie into a gas gathering system or where other gas handling systems are nonexistent or uneconomical. It has been a common practice to flare excess produced gas to eliminate the need for gathering or handling facilities. However, this practice wastes a valuable natural resource and is increasingly prohibited by environmental regulations. An alternative to flaring gas is to inject it into a different subterranean formation for storage and possible subsequent retrieval.
For high liquid production, an alternative to separation at the production facility is the use of a downhole submersible separator/compressor. However, submersible separator/compressors have a history of high failure rates in high GOR wells. Also, the gas compressor section of a submersible pump can be damaged if liquids enter it.
Thus, there is a need for a means to reduce the GOR in high GOR wells to decrease loading of gas handling facilities. There is also a need to provide an efficient system for reinjecting produced gas for pressure maintenance or for storage at wells where gas handling facilities are unavailable or uneconomical to construct. An additional need is to comply with environmental regulations that prohibit flaring of unwanted produced gas. A further need is to reduce waste of a natural resource.
For the foregoing reasons, there is a need for a wellsite compression/injection process in which produced gas is separated from liquid, for example, oil, in a high GOR-well, prior to reaching production facilities, and then compressed and reinjected via the well into a subterranean formation.
Accordingly, a primary object of the present invention is to reduce the GOR ratio in high GOR wells to decrease the loading of gas handling facilities.
Another object of the present invention is to provide an efficient system for reinjecting produced gas for pressure maintenance in a gas-drive reservoir.
A further object of the present invention is to provide a system for storing of gas produced at wells where gas handling facilities are unavailable or uneconomical to construct.
Yet another object of the present invention is to provide a means for storage of unwanted produced gas in compliance with environmental regulations prohibiting flaring.
Another object of the present invention is to reduce waste of produced gas, a natural resource.